Traveller's Diarrhoea

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Traveller's diarrhoea is a general term applied to the common problem of diarrhoeal illness experienced by travellers, usually in the first week or two of a stay in a foreign environment. It encompasses diarrhoea caused by numerous enteropathogens (bacteria, parasites and viruses) picked up from contaminated food and water in the new, foreign environment. It remains a major public health problem with significant morbidity.

Traveller's diarrhoea has been defined as "an increase in frequency of bowel movements to three or more loose stools per day during a trip abroad, usually to a less economically developed region".[1]

It is estimated that 20-60% of travellers will be affected by traveller's diarrhoea around the world. It particularly affects those who travel from industrialised countries to developing countries, especially tropical and semi-tropical destinations. The risk and aetiology are determined by the place of destination. The pathogen is often not determined but, where it is, the most common cause is one of a number of bacteria. Globally, enterotoxigenic Escherichia coli is the most common bacterial cause, with Campylobacter jejuni and Salmonella and Shigella species also often culprits. Rotaviruses and noroviruses are also common causes. Protozoa such as Giardia lamblia or Cyclospora spp. are more likely to cause persistent diarrhoea, lasting over two weeks.

Information about level of risk in individual destinations is available on the National Travel Health Network and Centre (NaTHNaC) website.[2]

High-risk areas: South and Southeast Asia, Central America, West and North Africa, South America, East Africa. (C. jejuni infection is more common in Southeast Asia, whereas E. coli is more common in South Asia, sub-Saharan Africa, and Latin America. Norovirus is common in Latin America and sub-Saharan Africa, and parasitic infection is more common in South and Southeast Asia.)

Intermediate-risk areas: Russia, China, Caribbean, South Africa.

Low-risk areas: North America, Western Europe, Australia and New Zealand.

Investigation may be required if diarrhoea persists for more than 14 days, or earlier if there is blood in the stool, fever or more severe illness.

Blood tests: FBC, U&Es, LFTs, ESR and CRP.

Stool culture including microscopy, culture and sensitivity and tests for ova, cysts and parasites.

Additional stool tests may be done, according to history and travel destination, whether stool is bloody, whether recent antibiotics have been taken, in young children aged under 5 (rotavirus).

Clostridium difficile toxin may be tested for if the patient has recently been in hospital or has taken broad-spectrum antibiotics in the preceding six weeks.

Further investigation with imaging or endoscopy may be required if there is severe tenderness or there are signs of severe colitis.

One study found that a raised CRP and faecal white cells were associated with bacterial infection but not parasitic infection.[4]

Management

The vast majority of cases will be managed at home with oral rehydration. Most are self-limiting illnesses, which do not require medical intervention. However, it is important to identify patients who should be managed differently. The state of hydration will need monitoring in all patients but particularly those with more severe symptoms and those at risk of dehydration.

Oral rehydration and home monitoring

This is appropriate for low-risk patients with mild or no dehydration and mild symptoms, who have favourable home circumstances. The young, the elderly and other higher-risk patients should be monitored particularly closely.

Racecadotril is designed to be used with rehydration treatment.[5] It reduces the amount of water that is released into the gut during an episode of diarrhoea. It is licensed for the complementary symptomatic treatment of acute diarrhoea in children (aged over 3 months) and adults, together with oral rehydration and the usual support measures (dietary advice and increased daily fluid intake), when these measures alone are insufficient to control the clinical condition. It is not recommended for use within NHS Scotland for the treatment of acute diarrhoea in children because there is insufficient evidence that it improves the recovery rate.[6] The Clinical Knowledge Summary (CKS) from the National Institute for Health and Care Excellence (NICE) does not recommend racecadotril in traveller's diarrhoea.[7]

Oral rehydration and consider admission

Mild-to-moderate dehydration can often be managed at home if all other factors are favourable and the patient can be reviewed. In patients at risk of worsening dehydration with severe symptoms or with other risk factors (the young, the elderly, those with immunosuppression or other comorbid conditions), admission should be considered.

Referral for possible admission in children should be considered for:[8]

Children younger than 1 year, particularly those younger than 6 months.

Infants who were of low birth weight.

Children who have passed more than five diarrhoeal stools in the previous 24 hours.

Children who have vomited more than twice in the previous 24 hours.

Children who have not been offered or have not been able to tolerate supplementary fluids before presentation.

Symptomatic treatment may be needed for logistical reasons, particularly whilst travelling. There is more evidence for efficacy and safety of loperamide; however, bismuth subsalicylate may also be used. Neither should be used if the stool contains blood or mucus, or if there is fever, and they should not be used for more than 2 days. Anti-motility medication is not recommended for children. (Loperamide should be avoided in those under the age of 12, and bismuth subsalicylate under the age of 16.)

Ideally where it is needed, antibiotic therapy should be guided by microbiology advice, with the benefit of the results of the stool sample and sensitivities determined thereby. Where empirical treatment is needed, ciprofloxacin 500 mg bd for three days is the usual choice. However, in travellers from South Asia and Southeast Asia, quinolone resistance is common, and azithromycin (off-licence) is the preferred choice. (500 mg daily for three days in adults and children over 45 kg.) Azithromycin is also used where quinolones are contra-indicated, such as in pregnant women or children.

Studies show these antibiotics reduce the course from an average of three days to an average of 1.5 days.[1]

Complications

Traveller's diarrhoea is typically self-limiting and serious complications are unusual. The most significant effect is that of the illness itself and the associated morbidity and disability. By definition it can be disruptive to people travelling for whatever reason, whether for holiday or business. Complications associated with dehydration may occur in severe cases, and other unusual sequelae include toxic megacolon, hepatic abscess, sepsis and bowel perforation.

Postinfectious irritable bowel syndrome (IBS) occurs in up to 30% of cases.[9]

Food and drink hygiene advice

Although there is no evidence that advice on safe eating and drinking affects the rate of traveller's diarrhoea, it is known that most cases come from food or drink. Therefore advice about the following remains standard for travel to high-risk countries:

Boil or otherwise purify drinking water. Use only bottled or boiled water for ice cubes, brushing teeth and washing food.

Eat only thoroughly cooked food.

Avoid raw seafood.

Peel fruit and vegetables before eating them.

Be wary of food in markets or buffets, which has been out for some time.

Avoid ice cream, unless from a reliable source.

Wash hands regularly, particularly when handling food or eating and after using the toilet, etc.

Chemoprophylaxis

For most people antibiotic prophylaxis is not recommended, due to the self-limiting nature of the illness and the side-effects and resistance potential of treatment. It should be considered for people at high risk of getting traveller's diarrhoea and who are vulnerable to complications. For example, those travelling to high-risk areas and who are likely to contract infection through the type of trip, who are:

Immunosuppressed (on chemotherapy or other immunosuppressant medication, those with advanced HIV).

At high risk of complications (eg, those with gastrointestinal abnormality or disease).

Vulnerable due to age (babies, infants, frail elderly) or comorbidity.

Undergoing a critical trip where the illness would have a severe impact on the purpose of the trip.

Where continuous antibiotic prophylaxis is advisable, options are ciprofloxacin, norfloxacin, rifaximin or bismuth subsalicylate. Of these, ciprofloxacin is the most effective.

Standby antibiotics

It may be helpful for some people travelling to high-risk or medium-risk countries to have a supply of "in case" antibiotics to take should they develop traveller's diarrhoea. This may be particularly helpful for those who are going to be in remote areas with poor sanitation and lack of access to healthcare, or for those who are trekking or travelling continually. A short course of antibiotics is known to reduce the length of the illness. Choice of antibiotic will depend on the area and likely risks and resistance, as well as individual age, pregnancy status and comorbidity. Usually ciprofloxacin 500 mg bd for three days, or azithromycin 500 mg daily for three days is the option used. Azithromycin is used off-licence for this indication, and either would require a private prescription. An alternative is bismuth subsalicylate but this cannot be used under the age of 16, in pregnant/breast-feeding women or in those with salicylate sensitivity. NICE CKS does not advise rifaximin in this situation due to its limited efficacy. Taking loperamide in addition to the antibiotic treatment seems to speed the rate of cure.[11] There are concerns, however, that this may predispose to colonization with extended-spectrum β-lactamase-producing Enterobacteriaceae.[12]

Other options

There is some evidence that probiotics may help prevent traveller's diarrhoea.[13, 14]However, it is not yet known which preparation and what dose are optimal and these are not currently a standard recommendation.

Collaboration between local governments and public health researchers could improve hygiene in high-risk areas and reduce risk to travellers.

Vaccines and immunoprophylaxis may be helpful in certain circumstances.[15] Vaccines are available for Salmonella typhi and rotavirus. An efficient cholera vaccine is available and gives some cross-protection against E. coli enterotoxin. It is, however, only marginally effective against traveller's diarrhoea. One study reported that ten people would need to be vaccinated to prevent one case of traveller's diarrhoea.[16] The typhoid vaccine is currently the only one routinely recommended for travellers. Vaccines against enterotoxigenic E. coli are in development and are a World Health Organization (WHO) priority.[17]

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